Journal article
Galaxies with background QSOs - I. A search for strong galactic Hα lines
Monthly notices of the Royal Astronomical Society, v 423(4), pp 3692-3708
Nov 2012
Abstract
A search for emission lines in foreground galaxies in quasar spectra (z
gal < z
QSO) of the Sloan Digital Sky Survey data release 5 reveals 23 examples of quasars shining through low redshift, foreground galaxies at small impact parameters (<10 kpc). About 74 000 quasar spectra were examined by searching for narrow Hα emission lines at z < 0.38, at a flux level greater than 5 × 10−17 erg cm−2 s−1, and then confirming that other expected emission lines of the H ii regions in the galaxy are detected. The galaxies were deblended from the quasar images to get colours and morphologies. For cases that allow the galaxy and the quasar to be deblended, the galaxies are blue (0.95 < (u−r) < 1.95). Extinction and reddening through the galaxies are determined from the (g−i) colour excess of the quasars. These reddening values are compared with the flux ratio of Hα to Hβ, which reflect the extinction for an undetermined fraction of the sightline through each galaxy. No trends were found relating E(B−V)(g−i), impact parameter (b), and (u−r) for the galaxies or between E(B−V) derived from (g−i) and that derived from Hα/Hβ. Comparison with previous studies of quasar absorption systems indicates that our sample is more reddened, suggesting disc-dominated absorber galaxies. Measurement or limits on galactic, interstellar Ca ii and Na i absorption lines are given from the quasar spectrum. No trends were found relating the Ca ii equivalent width W (Ca ii) or the Na i equivalent width W (Na i) to b, but a correlation of r
s=−0.77 (α= 0.05) was found relating W (Ca ii) and E(B−V)(g−i).
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Details
- Title
- Galaxies with background QSOs - I. A search for strong galactic Hα lines
- Creators
- Donald G York - 1Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USALorrie A Straka - 3Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208, USAMichael Bishof - 1Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USASeth Kuttruff - 4Department of Physics and Astronomy, Carthage College, Kenosha, WI 53140, USADavid Bowen - 5Department of Physics and Astronomy, Princeton University, Princeton, NJ 08544, USAVarsha P Kulkarni - 3Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208, USAMark Subbarao - 6Adler Planetarium, Chicago, IL 60605, USAGordon Richards - 7Department of Physics, Drexel University, Philadelphia, PA 19104, USADaniel Vanden Berk - 8Department of Physics, St. Vincent College, Latrobe, PA 15650, USAPatrick B Hall - 9Department of Physics and Astronomy, York University, Toronto, ON, CanadaTimothy Heckman - 10Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USAPushpa Khare - 11CSIR Emeritus Scientist, IUCAA, Ganeshkhind, Pune 411007, IndiaJean Quashnock - 1Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USALara Ghering - 1Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USASean Johnson - 1Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
- Publication Details
- Monthly notices of the Royal Astronomical Society, v 423(4), pp 3692-3708
- Publisher
- Blackwell Publishing Ltd; Oxford, UK
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:000306003600054
- Scopus ID
- 2-s2.0-84863626329
- Other Identifier
- 991014877907004721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Astronomy & Astrophysics